1. Field of the Invention
The invention relates to a start-up control device and a start-up control method for an internal combustion engine equipped with a fuel injection mechanism (in-cylinder injection-purpose injector) that injects fuel toward the inside of a cylinder at high pressure, or an internal combustion engine equipped with a fuel injection mechanism (intake passageway injection-purpose injector) that injects fuel toward the inside of an intake port, or an internal combustion engine equipped with both of these fuel injection mechanisms. More particularly, the invention relates to a technology of operating a fuel pump before cranking.
2. Description of the Related Art
There is known a gasoline engine that is equipped with a first fuel injection valve (in-cylinder injection-purpose injector) for injecting fuel into the combustion chamber of the engine and a second fuel injection valve (intake passageway injection-purpose injector) for injecting fuel into the intake passageway, and that selectively injects fuel via the in-cylinder injection-purpose injector or the intake passageway injection-purpose injector in accordance with the rotation speed of the engine or the load of the engine. A direct-injection gasoline engine equipped merely with a fuel injection valve for injecting fuel into the combustion chamber of the engine (in-cylinder injection-purpose injector) is also known. Furthermore, a gasoline engine equipped merely with a fuel injection valve for injecting fuel into the intake passageway (intake passageway injection-purpose injector) has been known for a long time.
In a high-pressure fuel system that includes an in-cylinder injection-purpose injector, fuel whose pressure has been heightened by a high-pressure fuel pump is supplied to an in-cylinder injection-purpose injector via a delivery pipe, and then the in-cylinder injection-purpose injector injects high-pressure fuel into the combustion chamber of each cylinder of the engine.
A diesel engine having a common-rail type fuel injection system is also known. In the common-rail type fuel injection system, the fuel whose pressure has been heightened by a high-pressure fuel pump is stored in a common rail, and the high-pressure fuel is injected from the common rail into the combustion chamber of each cylinder of the diesel engine by opening and closing an electromagnetic valve.
In order to bring fuel associated with the engine to a high-pressure state, a high-pressure fuel pump is used in which a cylinder is driven by a cam that is linked to a crankshaft of the engine. Incidentally, an engine equipped only with an intake passageway injection-purpose injector does not include such a high-pressure fuel pump.
In any of the aforementioned engines (an engine equipped with an in-cylinder injection-purpose injector and an intake passageway injection-purpose injector, an engine equipped with in-cylinder injection-purpose injector alone, and an engine equipped with an intake passageway injection-purpose injector alone), a problem as stated below occurs when the engine is started again after having been left in a stopped state.
In any of the engines, the piping from the fuel tank to the injector is provided with an oil-tight structure. However, if fuel leakage occurs due to bad sealing, or if a foreign matter is caught in the fuel injection hole of the injector, fuel leakage from the injector occurs. Therefore, from the state where the engine is stopped, the pressure declines (the pressure of fuel declines below the saturated vapor pressure (there is a relevancy to the temperature of fuel)), the reduced-pressure boiling occurs, so that vapor occurs in the piping.
Furthermore, since the high-pressure fuel pump inevitably has a clearance of a pump plunger due to its structure, fuel leaks through the clearance. The fuel that has leaked through the clearance is returned to the fuel tank (atmospheric pressure) via a return pipe. Therefore, the pressure also declines from the state where the engine is stopped, so that the reduced-pressure boiling occurs and therefore fuel vapor occurs in the piping.
If fuel vapor occurs in the fuel piping as described above, the fuel vapor impedes the pressure in the fuel piping from promptly rising to the feed pressure, thus deteriorating the start-up characteristic of the engine. In any of the foregoing engines, a cause of the occurrence of fuel vapor is that the pressure in the fuel piping declines during a stop of the engine.
Japanese Patent Application Publication No. JP-A-6-173806 discloses an injection device of an internal combustion engine which avoids an event where normal injection of fuel from an injector becomes impossible in the case where the pressure in the fuel piping declines during a stop of the engine. This injection device of the internal combustion engine is an injection device of the internal combustion engine wherein a fuel injection valve that injects a desired amount of fuel into an intake passageway of the internal combustion engine by appropriately controlling the communication between the fuel supply opening and the fuel injection opening and a fuel pump that generates a fuel pressure by pumping up fuel from a fuel tank are interconnected in communication via a fuel path, and a fuel pressure regulator that keeps the fuel pressure in the fuel path below a predetermined value is provided in the fuel path, and wherein the fuel pressure supplied to the fuel supply opening of the fuel injection valve is kept at a constant level. The injection device includes a start-up prediction portion that detects a predetermined phenomenon that occurs prior to the start-up of the internal combustion engine, and predicts a start-up of the internal combustion engine on the basis of the detection of the phenomenon, and a fuel pressure raising portion that raises the fuel pressure in the fuel path if the start-up prediction portion predicts a start-up of the internal combustion engine.
According to this injection device of the internal combustion engine, when a predetermined phenomenon prior to a start-up of the internal combustion engine is detected (e.g., when it is detected that the driver's seat-side door is opened through the monitoring of the opening and closing state of the driver's seat-side door while the internal combustion engine is at a stop), the pressure in the fuel path is heightened in advance so that whenever the internal combustion engine is to be started up, a predetermined fuel pressure is supplied to the fuel injection valve. Therefore, unlike the related-art devices, the fuel injection amount at the time of starting up the internal combustion engine does not become unstable, so that good start-up characteristic of the internal combustion engine and good operation stability of the vehicle immediately following the start-up can be secured.
However, in the injection device of the internal combustion engine disclosed in Japanese Patent Application Publication No. JP-A-6-173806 mentioned above, when the driver's seat-side door is opened, it is judged that the engine is to be started, and the fuel pump is operated for a predetermined time to heighten the pressure of fuel in advance. However, operating the fuel pump for the fixed time uniformly as mentioned above does not appropriately corresponds to the actual state of occurrence of fuel vapor, and the fuel pump may be operated for unnecessarily long time. If this happens, there arises a problem of reduction of the service life of the fuel pump, or a problem of noise and vibration due to the unnecessarily long-time operation of the fuel pump prior to the start-up of the engine.